The present invention relates to a semiconductor apparatus and a portable terminal apparatus, and particularly to a semiconductor apparatus including a quadrature demodulator and a portable terminal apparatus using the semiconductor apparatus.
Digital portable telephone apparatus using such systems as CDMA (Code Division Multiple Access), GSM (Global System for Mobile Communications), and PDC (Personal Digital Cellular) have recently been spreading rapidly as portable terminal apparatus. Also, development is proceeding to provide a portable terminal apparatus typified by the digital portable telephone apparatus with a GPS (Global Positioning System) function.
When the portable terminal apparatus is provided with the GPS function, the portable terminal apparatus may simply include the function of a conventional GPS receiver as it is. However, this results in a complex configuration as well as a large apparatus body and high cost of the portable terminal apparatus. Therefore, it is conceivable that the configuration of the portable terminal apparatus may be simplified by using part of circuits in a signal processing system of the portable terminal apparatus also for GPS reception.
The receiving and demodulating part of the portable terminal apparatus, for example a digital portable telephone apparatus uses a linear amplifier and a quadrature demodulator (see Japanese Patent No. 3003839, for example). On the other hand, a GPS receiver uses a nonlinear amplifier and a digital signal processing circuit to demodulate a received signal (see Japanese Patent Laid-open No. Hei 8-23577, for example).
When the sharing of circuits by the receiving system of the digital portable telephone apparatus and the GPS receiving system is considered, it is desired to share a section from a baseband amplifier to an input of a digital signal processing circuit. However, the digital portable telephone apparatus handles a quadrature modulated signal, whereas GPS handles a BPSK (Binary Phase Shift Keying) modulated signal. Accordingly, the digital portable telephone apparatus and GPS use different demodulators and different signal level diagrams, and therefore some measures are required on the GPS receiving side.
More specifically, when a BPSK modulated signal of GPS is to be demodulated by a quadrature demodulator, a conventional IQ interface system requires that the BPSK modulated signal of GPS also maintain linearity and a dedicated bitmap logic circuit be provided. Therefore, a complex control system is required, thereby limiting reduction in power consumption and decreasing the degree of freedom of design of blocks to be used in conjunction with the receiving system of the portable telephone apparatus.